Why was the Yarkon River polluted during the late 20th century?

During the latter half of the 20th century, the Yarkon River in Tel Aviv–Yafo suffered from severe pollution caused by the discharge of sewage and other waste.1

Additionally, the river's ecological health was significantly impacted by the implementation of the Yarkon-Negev Project, which began in 1955 as part of the National Water Plan. This project led to a substantial reduction in the river's water levels, which contributed to the increase in pollution levels. Since the 1990s, extensive efforts have been undertaken to rehabilitate the river and restore its role as a recreational space for the city.21